1. Field of the Invention
The present invention relates to a check valve for micro electro mechanical structure devices (MEMS), and in particular pertains to a check valve which is adapted to be employed in connection with micro electro mechanical structure devices which are intended to be employed with the use of high-pressure fluids constituting working fluids.
2. Discussion of the Prior Art
The utilization of check valves in the most diverse designs and configurations thereof is well known in numerous and essentially unrelated technologies. In essence, such check valves which are utilized in connection with MEMS devices employing supercritical fluids are adapted to diverse potential uses, including being incorporated into micro pump systems and hydraulic circuit systems, wherein the combination of such systems and MEMS devices may provide micro refrigeration and heat exchanger structures.
In addition to the foregoing applications, the use of MEMS devices is adapted for integration thereof into processes for producing semiconductor chips and/or related electronic components. However, physical limitations which are evident through the introduction of fluids within the MEMS devices are caused by the surface tension of the fluid within the extremely small sized structures. Consequently, the use of supercritical high-pressure fluids which are combined with a check valve as a component of the overall structure and system enables the introduction of the fluid in order to fill the MEMS device and, then to be able to lock in the fluid at the required operating pressures. These devices become active when the working surface pressures and temperatures are elevated, causing a closed-loop pumping system, or a hydraulics and/or refrigeration loop to initiate operation.
Ordinarily, the loading or charging of MEMS devices with a supercritical fluid may be achieved through the intermediary of a processing cycle with a supercritical pressure vessel, and wherein the device is constructed with the incorporation of a suitable check valve which is initially in an open (through-flow) position at atmospheric pressure. Upon a pressure chamber of the device containing a workpiece which is to be treated being charged with a fluid to supercritical temperatures and pressures, that particular fluid will then be able to flow into the MEMS device due to an absence of surface tension in the fluid while in the supercritical phase. Thereafter, after a specified period of time, the chamber pressure is relieved, and the pressure drop will cause the fluid in the MEMS hydraulic system to attempt to escape, causing the check valve to close and thereby trapping the fluid in the structure. Thereafter, the check valve being at atmospheric pressure, will be permanently locked into the system.
For instance, the uses of cryogenic microcoolers employ a condenser, evaporator, flow restriction and counterflow heat exchangers have been described in article by Johannes Burger, et al., and titled xe2x80x9c169 Kelvin Cryogenic Microcooler Employing a Condenser, Evaporator, Flow Restriction and Counterflow Heat Exchangesxe2x80x9d in the 2001 IEEE, pages 418-421, presented at the 14th IEEE International Conference of Micro Electro Mechanical Systems, Switzerland, Jan. 21-25, 2001.
Accordingly, in order to be able to accomplish the foregoing functioning in a simple and advantageous manner, through the incorporation of a novel check valve which is adapted to be incorporated into systems with MEMS devices operating with supercritical fluids, the present invention provides for the check valve being equipped with a bypass channel including a freely moveable plug structure which, in the open position of the valve enables the ingress of supercritical fluids under high superatmospheric pressures, and subsequent to the filling of the system, let down to atmospheric pressure, causes the plug to be moved into a permanent valve-closed position.
Pursuant to another embodiment of the invention, the check valve may incorporate a flexible valve element in the form of a flap member, which in the open position enables the flow from a narrow channel into a wider channel for loading the particular system with a supercritical fluid under a superatmospheric pressure, and subsequent to the filling of the system and let down thereof to atmospheric pressure, enables the flexible plug or flap member to provide a sealing element between the wide inner channel and a narrower outer channel to form a permanent closure for the MEMS device in which the check valve is installed.